DTIC ADA419949: UAV Aerial Refueling - Wind Tunnel Results and Comparison with Analytical Predictions

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by  Defense Technical Information Center

AFRL-VA-WP-TP-2004-300

UAY AERIAL REFUELING — WIND.
TUNNEL RESULTS AND
COMPARISON WITII ANALYTICAL
PREDICTIONS

William B, Blake
Sdward G, Dickes

JANUARY 2004

‘Approved for public release: distribution is unlimited,

‘This material is declared a wark of the US. Govert
protaction In the Untted States.

yt and is not subject 10 copyright

AIR VEHICLES DIRECTORATE
AIR FORCE RESEARCH LABORATORY

20040218 149

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Jamar 7008 Conference Paper Preprint
UAY AMRIAL REFUELING — WIND TUNNEL RESULTS AND. Instouse
‘COMPARISON WITH ANALYTICAL. PREDICTIONS [se erawrnuneeR
NA
6 AUTHOR “Ed, PROJECT HUMBER
‘WillesaB. Blake (AFRLIVACA) NA.
Bdviad G, Dicks (Bible) Se TANNER
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{a WORK tii ER
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[I ‘Conlavence paper oe peorented arthe AIA Atmaspherio Hight Mechanics Conference, Providence, KI, August 2008,
‘his material x declced a wouk of te U.S, Government aud isnot subject to coaynightpeotetion inthe United Ses

Th aastmacr
Regis ams wind net st ofa dcfty wirg UAV behind 9 KC-135R ure present urd compared vilbprdietions
fom a planur vortex Itice unde, Both lhe predictions and data show wake interterenoe effects on the UAV that vary
prlfcently with lave vers! and vertical postion, and weakly with relaive mgituinal oii. Prefered rend ar>
‘cella forall ree and onents except fr drug, und magnitules ure reusonably sell preted. The diribution oF ER
hetween the Linker wing acd ale hwo havea suorg effet cn he eveiveraetodybaaics

‘Aetialsebeling, wind mame! testing

7 SECURITY CLASSIFICATION OF: 7 LTATION 7B. NUNEER | "is, NAME OF REGPOHSIELE PERSON Hors)

a. feporr |b ABSTRACT |<. THSPAGE] OF AOSTRACT: foraces| "” Wilin 2, Blake

Trheifet| Doclasifed |Thetasitod SAK 14 | in. TELEPHONE NoBER pce Bran cass
[phone]
AMAA 200:

UAV ABRIAL REKULLING - WIND TUNNEL RESULTS AND COMPARISON WITH
ANALYTICAL PREDICTIONS.

William H. fluke”
Air Fove Research Laboratory
‘Weight Patterson AFB OH 45433-7534

Ellard G, Dickes
ihre Applied Research
Hampton VA 23666

ausreact

[Rezo hom a wind mane! tart ofa deta wing UAY
bebiod 2 KC-135% are presented an compared with,
peeditions fer a planar wares latice code, Bott
the predictions and data sow wake interieerce
feos on dhe WAV dh vary signiicanly with
relaive lated und versal position, and weal with
slave lnginuinal position. Predicted eende are
cevcolla forall free and monuata except for dea,
‘aud naguiades ae eascuebly yell pedicle. The
sdsibmtin of ER botveea the taker wing and tli
show to bate & mong ellet on the seveive:
seradynomics.

NOMENCLATURE

A Aspect ro

Wingspan

Gr, Uttooeticient

Gp Dag encffcine

Gy Ralling nome oveffcient

Go Pvbiog moment coefisiet

Cu Yavtug someatcoeivient

Cy Side farce eotfcient

x Longituliad distonce fom UAV
AY eg. postive forward

y Laer distance fom UAV eg. 12 tanker
6. posilve right

7

= Verial dince fom UAY eg. 12 teokee
eg, pnstive down

Angle of anack

© Astgyse Lnginer, Assit ello ADA

s+ __Astsnace Bninsee Sind Mester IAA,
‘Tisgpir ls dent workel ie US. gotumcl ane
stron nerrih proton athe Used Sas

INTRO

ICTION

Fer over 501 year, the USAR bas employed acral
refueling wo inves the ange of sai, Aeris)
refueling alia reduces forward baring requirement,
creates response ties foe eflieal targets, and
Inereowes lotr tne for sunvillimce sire. The
‘ic Foros Reseach Laboratory, in patnersbip wi
DAREA, NASA and Rocing, is curetly musing a
rrvgrim ty derunscale aoa celal of a
TICAY “class UAV. UCAVE under cument
development by ke Ai Force and Nuyy wo
surtvabla designs capable of delivering homh Toate
in excess of 1600 Ib. Prototype aircraft have been
fing by brads Bocing (X-d5) and Mornay (17.
Alough compumble in size to Sightor aiscrak,
TIGAYS ave geoeially Lighter vith craler moments
of icons. This aggravate the effects of nztnfonec
bebiad the ler thal ke CAV will encounter
Dafoe, during and afterscfaling

“The flow survey Hy within tho Langley 30360 Ful,
Seale Wind Turwel wat movie several yes 380 fg
allow ‘eating of multiple aicraR in formation’!
Sevstal wind tunel tats of ceiver aircraft ebind a
CILISK tanker hive sinve been completed fo it
faci, Tho pinay objectives ofthe ean a's
‘as 10 asseas the stably and vento] charters
‘af the UAV in the tater wake and ta develop 3
‘databors for sinwlalon end oocrol lw development.
"This paper with disease ronan from one of these
lets, and compare the tet results wilh prions
senztated bya vortex latice code.

Previous studies ave chown good ygeement
benvecn worter legion pveditions and we
intecteenve effects on dowmizenm siti. Rosson

ASC - 03-3283
measred veke- Seduced effets un sets sels of
igoaled wings tht ere soparted Ienpainay by
many wing spans. He showed tht the varie tice
toathod de extcemely secorte for proditing wa
Snduced KD and elling moraeat when the span of te
downstream wing ix sbetutTly less dhan tat of de
wake generaling Wisg. lay ct al investiznted
fncations ‘ypical of aerial refueling with the
reoivcr fer th up wing span dosmstream of the
tanker. Tose fet wore conducted in a sell wind
loan wth a wingopan (© tunnel wid rain of 0.7
Significant wall iulrivence effects were uncovered
Ty taking measurements in both open au closed test
seclions, ‘They found good agicement with vortex
Tate predictions when compared to tetr open test
section resis

DISCUSS

{WEND TUNNEL SET-UP

“The wind tunnel tests were conducted inthe Langley
Full Scale Wind Tunnel (O%60), aported by Ol
Tino University. "ihe tanker was a 113 scale
KC-I35R (Figne 1. Pour sects fs were sed (©
stale th engive these The eanker was attached
‘atthe tp of ts fuzclage to he Do sorvey cariags
‘sed in he Langley roel (Figae 1). ‘The fop moat
sorngement mdninars sg itlerTsence feos hen
the receiver is in the nominal refueling positon
below the tanker Relative posiian betwern the
wanker and receiver was achioeed ty moving the
fsorvey caniage. The mmceiver was’ a 1/13 seate
Locked (ales sivratt eonsiztne of 2 65 desree
delta wing witb a aevlools tilling edge wth swoep
angles oF 25 dgrocs (Figure 1}. eis single engve
sdsign with ate narrow ales on th ler surface
“The ites were blacked for fhe presect (2S. Teas
conte from tke boom wa post that was sed to
‘ho tunne!focr (Figure)

Both sncrat were equipped with internal “6
component stuly gauge balaness. By moving the
tanker and keeping the received Lxod, all changes to
the receiver serafyaazvcs were due to the taker
‘wake and aot to small vaiaGons fb flow angulasty

Joo

Figue 1. KC-ASSR/UAV Gomory (ull scale)

Figwe 2, Wiod Tome! Moels ow Apparat

a were teen with The Lauer in four vertical
planes upstream of the reasiver (Figure 3). Bast
plane conscled of apguosinitely 200 pois in Oe
fates apd vertical diveton. Daa ware oly ten
wilh ie hacker tis right of the receiver, wha
tooking upttim, (hs, symewsay of the esl wat
sscumed. The faker wus set at an ange of tack of
2 dopsees shu boron) subir soning of -B
Segrce. This ocak in a tua Lift coefficient oF
(036, eamesponding na reference refueling cmon
(250,000 Ib at 28,000 A. The recive as rete a
fro angles of tick (4 and T deg) nt enc position,
This paper will uly show results forthe 4 eg,
ingle of atack rans. All rong sere conducted at =
‘unc dynatic presse of SpsE, which eanesponds
lo speed uf approximately 65 fee.

COMPUTATIONAL METHON

‘5 mliiedyotson ofthe pagar vuctex fcr cade
Hascos! wer ured to peediet the wake induced
effets on. the eat aie The mumter of
permissible vortex cleats was incess04 from 2000
fo alow fer hore: definition of multiple axa. A,
rogram wus als witon that anonnecally generates
Input les fox a user deGied set af tankerocever
Osiims, runs the cade for each pesto, ad sass
The rests. Tota computation tne fr a ran of 130
‘elaive poutions was about 4 hour: onan SCI igo
Tvwarktation.

‘The tanker ns aedeled with 2100 eloments, de
recciver with 450 slemente. Cosine speing of the
‘lowers was ved inthe choriree dicoton. Fvea
spicing of the elements was wed ia the spans
‘retin. This is necessity in ends fo corre erect
ligament of vorix filamcnss and cons) pola
‘whe the aera overlap fn the iter! diection, An
clement width of 15 iaches (ll sale) wae chosen
{ht Lott vehicles. ‘Thix zoe. in come. slight
approximations to 2 “tetual geomeby. A
expan uf the acta! end tundeled span is hewn
fn Table 1. The TASCIS repreeniaion of dhe
‘eke is chown a Figure

Wakdel | Aca
spantiy_[ gun (a
KEG yiee [1560 [1570
Kesey —pst0 | 510
AY 450 [aso

TTANTET ASC Goomety Appewiaaton

Figure 4 HASCSS lnc model

Wake indoced effeots area foneion oft Hf of the
wake generating oie Bence it in very important
atch the meeamoed HD uf Ue toker sith the
TIASCOS model, HASCOS unos single ale of
tack fx bod sucflaehich rues ajusments 9
wing incidence angler in order co sch be tet
conditions. Two mluxts were sudied for madstng
hicles, us own in Table 2

Wind | HANS [mae
tunel | a

ROLE ose |i |

KeassaoA 2

KCA95 wig amber | “yes

KES wing osdegse [2 | a6

C135 mltecdesce [|b

[av Aca. 473

UAV wogmeings [0 [2 Ja

"TAIN 2 = MARUIS Modeling Opto

Matods A and were found to give identical
raul, s0 Motied A was weed for all subsequent
‘kul

RESUL1S-LONGITUDINAT,

Figure $ shows dhe variston ja wake iaaed Kil om
the cescver as a Guotion of feral spacing for 60
Tongiludioal spacings. Longinuioal spacing
rmoasured fam the eg of he take lothe eg. af the
receiver, The closest epacing shown Gub=D.85)
reprseat the "pre-antes! pest, wits ae of
he tcciverayprexinaely DU fi (ul ole) fom ie
aflend ofthe tinker. Atthe fethost ing (2-4),
the receiver is 300 (fll eae) behind of Te ok.
Vera spacing i also measured tome 1 0,
vertical epasig of 21m indicate that tp seein ie
bout 2 (UM seal) above the wing root and §
(Gill sale) clow the veng tip and horizontal tl
Lateral spacing (Sis) rvescs he rela lateral
postion between the veel, non-dinerscnilized
by the span of ke take A exlus of O means that
the esttaines af ts vebicles are wigne, A vale of
10.5 means thal the mse of ae aeeiver ie ligasd with
the Hef! wingtip oF the tanker. The wing tps are
ayied at value of 0.64, beyond dl, there is m0
‘overlap between the configurations ie the ltrs)
rovion, ‘Both the prediction and daa show almost
re effect of lungitdinal spacing, while lateral
spacing bas a very large effect, Wi the velcles
‘Migned, u avell Lid inctease i provioted and
tuoasared, a te otra spcing incrosos, nereasiog
downs ig evident chat peas ula sparing of 03
sane, The downsvach decreazes und upwash
enecenteed cuthour of te i. The ictease in HB
‘wih the vehicles aligoed ects fom she lege
owed on the borizonal tal ofthe exer required
ar rim, This enuses upwrah dieehy beneath che tat
aad iis tho wing dawmnwash outboard of the tai
‘Ths is depivied fn Figure & The KC-T3S design
dete tothe carly 2950s and hus bigh degree of
tle sbi

(ra ne eneen Ay
igure 5. Compacicn of pedir and smacaed
‘wake induced Hof.

The effect of tim ta doflostion was assessed
computationally and theres is show in Fig.
"To mutch the overall (tal tanker fit wih diforcat
tail deflections, the torker wing incidence “wat
oid. Figure T how that with no tall defletion,
lage LR loss is preseal until dw tecaiver
approsehos de tenksr wig ip. eau shone Het the
[eal tne ie Larger forthe downloaded til when
tho eeccver is jos ontioard of the til and tho tal
ddoxwash ic aldo ote lng doses

oO [ FF G
te tis iy ee
quer emt

TT TT Ie

nur te tty, ta
devoueah eget,

‘igue 6. Efcot oF tai it on tanker wake 26 view,

Lauran conn AFC yb
Figure. ttt af take al deflection on Wake
induoed fil, 20.85, 20-0,

igure & shows: the induced Lil fer to vertical
syacings as finoon of lateral pacing he
ditional vertical spicing shown (2b=0225)
‘oneespends the refsling poston {fer bao ype
refuting). The magnitude of tke lif change i
‘reduced at all spanwise Iocafons and the smal i
Inoreare fore in-plane (2-0) cate is now a sel
deere,
lreemenl ,

Uiwaloitnns Sotvan Aa ys
Figure. Compas of predicted ind meusured
‘wake ined It 08085.

Figure 9 shows the effect of vertical apacing at a
lal spacing of ye) (vehicle ceafertines afgue
The eect of teal dowmload canbe lout cee in
thie Sigue. The recevee if érooty blind the
Dati il at a vertical spacing of afb=0.08,
ssc sth location of de pose inersse in HA. AS
the rocciver moves wy Gun ths pus on eee
lrocion, ti it inuod Vit doscensea. Asis eves
rignticazly downwurd the IN bss decreases and
anmpllicly approaches mare. At ie boom
Tifbeliag poston, the Ft lus is underpreisied by.
aboot & factor of eva. The reason for a6
Sscrepuncy is not known at this Gace, Somve of i
nay he dn nthe eft of tho cocling ton, whish
‘war ont inched in the TLASC9S mol

cei i,
3

oak

Figure 9. Comparten of prodictd and measured
‘wale induced if y-0,sib-1 5.

Fiynwe 10 congas he measured and predicid drag
surterenis we fonction of liza spacing for v0

vena spucags, Tiguie LU shows the etfon of
wetieat spacing om dog. Both Bzurva abow poor
greemeol betwee le maeasired and. prodieted
hss, snd Jn many cases the sign is dneorocty
predicted, Nuch uf this is undoubtedly due 10
‘ison effor,shich HARCSS ignres,

eration San to
ewe tC reeds eae
eel gen
. _
° oft
lo
Heee

Fipwe 31. Comparison of predicted and measured
wake indeed dog, yO, 001.5,

Predicted and measured piling moe ineresas
a compared in Figice 12 as a function of fuel
sting and Figue 12. ac 9 fonction of vance!
racing, Both the prediction und dala show five
CGstines peaks as Ukr spasing i iacreused fa he
inplme case. Toe mugritules of the peaks,
ower, ae underprodiend ia every case, The
peaks appeue te cunespul o the the wing tps oF
‘he roster area ropfons of ether usin uprash
‘or dowowash, Arte rficling pion beneuth the
siren (/b-025). the moments are Wey soll ba
‘yell rcdicted, A weiie! pacing fs vce gare
13), to peaks dus to tho tanker ail are evident,
wish ae bath easpaably vel preicled

insullicienl dota ke detrine whether this iafletion
print ereaL

g A

fe 4
he
2 tare Baan o eit

[eheraloitnes Season Atom ye
Figure 12. Compavisn of prdicted and meoured
‘Wale induced pitching mament, /o-0.85,

i corms | = aware

Figure 12, Comparison of predicied ond asutet
‘wake induced pitching moment, yb

RESUETS - LA'TERAL-DIRECTIONAT.

‘The effet of Leal spacing 07 indoced rolling
orient a he to extreme lopgitudina spaclegs 1
shoo in Figure 14, As wil he iecd Hf, dere
viualy ng aftect of dovmstream spasing bu large
celiest of netol spacing, Fra tho woud and
magnitude of the induced rolling momcat ae very
‘well predicted. “The piaks corespond @ Oe
criedine of the DAV boing postioned dicey
bebiod the tip vonces of de taker tail and wing.
respectively. The slight inflection poi wits he
AY. at shout stb=D'3 comsspenti to the UAY
rossi, am ahve ty Below the plans of the tke
wing, esuling for the wing ditedal. "There

Liebenson lez
Figooe 4, Compas of predicted and measured
‘wal: indoced rolling men, 242.

‘The predicted effect of the taker tll sting is given
in Npure 15, Wi no el dcetin,thee is only
‘anc rolling momeal peek, which avisct trom the
lanker wing tip vortex. The peak wl is lower dae
tw the reduced Hi fom the tanker wing, ince tere
1a large al dowaload to overoome.

Eon
i 4

Hig 15, Bilt of tarr til deflection wake
{duced rolling moment, wh~0.85, 7-0,

Figure 16 shows the offoct of lateral spacing for ero
‘erie! piciies, The voting meraents ut te lowes
‘pacing (rfucling postion) are mur lower than the
place case and are well predkced. Figure 17
shaw the effect of verlical spacing wid the UAV
positioned just iaboan! of the wingtip. The peak.
movin! # aloe the eg. of the tanker due 1 The
Abed ofthe wing. Te pecdcton i excelent.
‘
Fen

&

tea Detanefatasen Ae ys
‘igure 16. Comparison of predicted and wacasured
vee indueod alin momen) arb.

ons

:

i

F sa

4
Bpoe
Ba

aes histo ca 7
Ripe 17. Compirison of predicted ant aes
rake iuduoed reling monent, tb=0.45,

‘Tho effet, of taeral spacing on indeed yaring
moment is showy ia Figure 18. To pwenide 0 Die
inp, tbe vertical sis om this plot i Monica,
fo dhe milling onus result shoum on Figs 14-16.
Very soull yung moments are found for dhe ie
plane caro anf no yowiag mveroent is found forthe
refveling position. This is presumably duct the ack,
fa vera eon the recetvor. Althovg smal, the
inplaae veiuhs sh a difecot igo than De
prsdicton when the receiver iz bxhind de taker
ving (¥[email protected]) This indicate thar oe source of the
yaving manent may Le illest ag from dhe
feo halves of de wing, uae the diag pregilone
were alu poor fir dhe implenae cose,

Upton Beteen
‘Figur 18 Comparison of padictel und measured
‘wake iviced yavang momen, xA-0.65

The offer of att spacing on induc side force is
shown in Figure 19. ‘The wen! i well preted for
both sigh, aldiough the overall magniaatog ae
sl une han Se ince feats by tne
9 20). This is pobably due to the lack ofa velial
‘ail on the cenfiguation.

Sa
i
bad

Used Ditech aah
‘igure 19. Comparison of preivied aad mene
‘wake indwed side ore, xD 85

CONCLUSION

Roms Gon 2 wind tunnel test of UAV aetil
tefiwiog ins eye-soals wind toamel buve beso
resented and comyarsd with predioloon fiom =
liar vowex lave cede, inthe longi axis
‘wake indoced effocts wor well prediced for ff and
Ditching monient and poeslypredetd for cag. Lit
and momen: ads worn extremely sell predicted
while peak magnitudes “were pica) wale
iotisted, an the Ieteslirenooe) anes, wale
induced effects on polling moment were very wel,
predicted, Wake effets on yasug moment and side
force were fond w be small, doe to the lack of a
atic it on the rocebver configpetion. The
‘somputational asalyls indiates thatthe dsibation
fof Gaker ft bersoen the canker wing aad tal i
four en bave w sigan effec

REDERENCES

1. Sisk, Michael, “USA. Studies Ways to
Rafuel Drones in Fight” Jane's Dofence Weekly,
anuvny 22, 200.

2, Gingas, DAL, Plager, 1. and Bloke, WB,
Seuaic ond Pyamic Wand Tunwel Testing of AUS
Vehicles in Close Proxinily." AIAA paper 2001-
4137, peeeated ul tbe ATAA Atmospheric Hight
‘Mechosles Conforence, August 2601,

3. asso, VI, “Vafidadan of Vorer-Tattoe
‘Methol for Loads on Wings in LiB-Generted
Waker,” Joural of Altera, Vol 32, No. 6,
[Novanhee-Decomber 1998, pp. 1254-1262,

4. Bhy, AW, Won MG, Lea, KA,
Jouma’a, M, “Laterd Asrodyuanic:Irsiference
etween Tooker and Receiver in AinD-Aie
Refueling” Foural of Aiteraft Val. 30, No.5, pp.
‘95-76, Sepentbar October 198,

5. Diekes, EG, and Blake, WE,
Tum Measurements of UAV Aecil Tel
‘Wake Inersnoe Blfots” ATA Paper 2004220,
rorented at the AIA Ataospherio Fgh
‘Mestnios Comfsronee, August 2004

6 Gill, WS, aod Donee, KM, "Divectioral
veo Bx Tailess Attra Uning AL loving Wing.
Tigh” ALAA paper O77, presatod a he AIA
‘Mbiosphere’ Hight Mectenies Confrene, August,
1997,

2. Albeight, AE, Dixon, C1, and Hogedu,
MC, "Modification und Validation of Concept
Design Aesodsuanis Prediction Mothods MASCSS
‘With VIXCHN, NASA CRAATI2, March 1996,